EN ISO 12085:1997 (ISO 12085:1996) is a Geometrical Product Specification (GPS) standard that defines terms, parameters and an ideal operator for the motif method of surface texture assessment by the profile method. The standard describes how to identify motifs on the primary profile, how to discriminate depths, how to combine motifs, and the measuring conditions required to generate reproducible motif parameters for roughness and waviness.
Key topics and technical requirements
- Motif concept: A motif is a portion of the primary profile delimited by peak points; motifs are classified as roughness motifs (length ≤ A) or waviness motifs (derived from the upper envelope line, length ≤ B). A and B are the conventional limits between roughness, waviness and residual form.
- Motif parameters: Defined parameters include mean spacing and mean depth of roughness motifs (AR, R), maximum depth (Rx), mean spacing and depth of waviness motifs (AW, W), maximum waviness depth (Wx) and total waviness depth (Wte).
- Depth discrimination:
- Minimum-depth method - divide the profile into sections (width A/2) and retain peaks whose depth exceeds 5% of the rectangle height.
- Maximum-depth method - level extreme peaks using H = Ej + 1.65·σj (Ej: mean motif depth; σj: standard deviation) to reduce influence of isolated high peaks.
- Combination algorithm: Four combination conditions (envelope, length, enlargement, similar-depth) are applied iteratively to merge motifs into the largest valid motifs; Annex A specifies a reproducible software method.
- Measuring conditions: Measurement conventions reference ISO 3274 and include recommended traversing, evaluation length, stylus tip and a requirement that the primary profile contain at least 150 vertical quantization steps. The ISO 4288 16% acceptance rule applies to motif parameters.
- Corrected upper envelope line: Used to identify waviness motifs and as an alternative to filtering (ISO 13565-1) for calculating bearing-related parameters (Rke, Rpke, Rvke).
Applications and users
- Practical uses: functional surface characterization, quality control, process capability analysis, acceptance criteria on engineering drawings, and multiprocess surface analysis.
- Typical users: metrologists, quality engineers, manufacturing/process engineers, surface-inspection labs, instrument and software developers, and drawing/product-definition specialists.
Related standards
EN ISO 12085 provides a filter-independent motif-based approach-complementary to ISO 4287-focused on motif depth and spacing to better link measured surface features to functional performance.